The present invention relates to a gas purging or injection device formed of fireproof refractory ceramic material and employed for introducing a gas, such as argon or other inert gases, natural gas, air or oxygen, etc., into a metallurgical vessel containing molten metal. More particularly, the present invention relates to a means and method for determining the degree of wear of such a gas injection device. Further particularly, the present invention is directed to such a means and method whereby the degree of wear of the device may be determined by optical examination of a surface of the device that is exposed to and worn away by the molten metal during operation of the metallurgical vessel.
A gas purification, purging or injection device of this type is disclosed in German DE-PS 31 42 989. This prior art device is formed of two refractory bodies having different degrees of gas permeability and different emission capacities, i.e. different emissivities, such difference being greater than 0.1. To determine the degree of wear of the device, after the vessel is emptied and while the device still is hot, the brightnesses of the two bodies are optically examined and determined. As the device is worn away, different geometric shapes are detected as a result of different emissivities.
However, this known arrangement suffers from a number of inherent disadvantages. Thus, the number of refractory ceramic materials that are suitable for use in a gas injection device are limited. This selection is even further restricted by the requirement that the emissivities of the two bodies be greater than 0.1. The result is a very limited and restricted selection of refractory materials. Furthermore, the detection and evaluation of such slight differences in emissivity is subjective and/or technically very expensive. Furthermore, the differences in emissivity of such refractory materials are measurable only over a relatively narrow temperature range, thereby requiring optical examination at a relatively specific time.